Friction stir welding (FSW) is commonly used to weld two or more work pieces formed of various metals, such as aluminum, magnesium, copper, titanium, steel and the like, one to another. FSW techniques may be employed satisfactorily to form welded lap joint, L-joint and/or T-joint.
During conventional FSW processes (including continuous and segmented friction stir welding), a FSW tool having a specific geometry is forced into, and traversed through the material to be welded. The key structural components of the tool include a shoulder and pin (sometimes called a “probe” in art parlance) extending outwardly from the shoulder. During the FSW process, the pin travels physically in and through the material along a joint line, while the shoulder is in surface contact with the material. Heat is generated by the tool shoulder by virtue frictional rubbing on the material surface it is in contact with and by virtue of the pin mixing the softened material below the shoulder. This mixing action of the softened material during the FSW process permits the material to be transferred across the joint line which forms a stirred region. Process variables affecting the FSW process may include rotation and travel speeds, tool design, orientation, position and tool forging load. Conventional FSW processes are disclosed, for example, by U.S. Pat. Nos. 7,225,966 and 7,240,821 (the entire contents of which are expressly incorporated hereinto by reference.
There is currently no known shop floor testing device or method near a FSW machine whereby welding parameters may be rapidly assessed in order to evaluate the quality of the weld. Instead, according to current practices, in order to analyze the quality of the welded joint during a research and development phase, several sets of FSW parameters (for example, welding speed, rotation speed and axial force) are established. A number of test specimens (coupons) formed of FSW welded components are thereafter produced in accordance with each set of FSW parameters in order to evaluate the welding quality associated with each set of parameters. Off-line testing such as metallography, tensile and pull-out tests are typically performed before selecting the set of FSW parameter for a given design criteria. As can be appreciated, this conventional iterative process is quite time consuming and is therefore quite expensive.
It would therefore be desirable if devices and methods were provided locally at a friction stir or other welding machine which could more easily and economically enable a manufacturer to verify and test the quality of welding joint strengths on coupons. It is towards providing such devices and methods that the embodiments disclosed herein are directed.
According to certain embodiments as disclosed herein, a device for testing weld strength of a test coupon joint is provided which includes a base defining a receiving region to receive and support a lower part of the test coupon and a clamp for positionally fixing the lower part of the test coupon to the base. A punch assembly having a head portion is provided so as to exert an axial force against the upright part of the test coupon to thereby determine weld strength between the planar and upright parts of the test coupon. A U-shaped receiver can be fixed to the base to define the receiving region. The base may include a rearward projecting portion to provide attachment and support for the clamping assembly.
The punch assembly may include a tail portion axially extending from the head portion for connection to a force actuator. According to some embodiments, the punch assembly may include a clamp piece connected to the head portion of the punch assembly for axial adjustments relative to a front face of the head portion so as to clamp the upright part of the test coupon thereagainst.
A guide assembly is provided according to certain embodiments and is removably connected to the base. The guide assembly in some embodiments will define a guideway for the tail portion of the punch assembly to allow for reciprocal axial movements thereof. The guideway will thus positionally capture the tail portion of the punch assembly to allow only axial movements thereof towards and away from the upright part of the test coupon. According to some embodiments, the base may include a forward projecting portion so that the guide assembly may be removably connected thereto. Certain embodiments of the device will be provided with a guide assembly comprised of opposed end blocks and a bridge section connected to and spanning the distance between the end blocks.
According to another aspect of the invention, a method is provided whereby the weld strength of a joint of a test coupon may be tested. In general, such a method will include clamping the lower part of the test coupon to a base of a testing device, moving a punch assembly of the testing device to exert an axial force against the upright part of the test coupon, and determining a maximum force of weld failure between the planar and upright parts of the test coupon.
According to some embodiments, the method may include providing a guide assembly which defines a guideway for positionally capturing a tail portion of the punch assembly to allow only axial movements thereof towards and away from the upright part of the test coupon. A clamp piece may be positioned relative to a front face of the head portion to clamp the upright part of the test coupon against the front face of the head portion. Such claim piece may be axially adjusted so as to positionally clamp the upright part of the test coupon against the front face of the head portion.
These and other aspects and advantages of the present invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.